Remarkably, localityHere we are referring to locality on the boundary. The implications of bulk locality were recently explored in [1]}. – in the form of an operator product expansion (OPE) – is yet another inherently two-dimensional property that
has been established for a class of boost eigenstates of massless particles [2]}.
These 2D-local OPEs originate from a collinear limit of momentum-space scattering amplitudes. As a result, the leading terms in the OPE inherit the same universality that is associated to collinear singularities in momentum space. For instance, the collinear splitting of graviton amplitudes is universal and does not receive loop corrections [3]}, while gauge theory amplitudes admit collinear factorization in which the splitting function is corrected at every loop order (see e.g. [4]}, [5]}).
